The goal of the proposed research is to determine the molecular weights and structures of the aromatic carcinogen-nucleoside adducts that are formed in human placenta and lung tissue as a result of cigarette smoking with matrix-assisted laser desorption ionization (MALDI) and time-of-flight mass spectrometry (TOFMS). Knowledge of such structural features will enable us to determine the aromatic amines or other polyaromatic hydrocarbons (PAH) in cigarette smoke that are most likely to bind to DNA and initiate tumor formation. The structures of the unknown aromatic DNA adducts isolated from human tissue will be inferred comparing the post-source-decay (PSD) product ion spectra if DNA adducts synthesized in vitro.